I just got myself a set op DN S1200s and I was also wondering how to use the D Link function.
There is nothing written in the manual about this function.
There should me a relay function but how can I activate this function?
Is it also possible , like on Pioneer CDJ 2000 and Denon HD 2500 to share files from one usb stick on both decks with the D link function?
I cannot find any info about this matter.

So, the 3700’s and the 1200’s are very much alike. I was reading in the owners manual for the 3700 that when the two devices are connected with a “crossover” ethernet cable no longer than “3 meters” long they will automatically link up and there will be an indicator in the display showing that. It seems that the songs themselves can not be shared across the link but data such as hot cues, loops, etc. can. My recommendation for understanding the full funtionality of D Link is to download the operators manual and do a word search for “D Link”. There is not one particular section that talks about it, rather it is spread out around the document. I hope this is helpful.